There has been conventionally available a flange coupling in which a pipe 4 is welded to the side face of a flange 3, for example, as shown in FIG. 1. However, the coupling of this type has a drawback of requiring a welding process. Therefore, there can be used a flange coupling in which an L-shaped pipe 4 is installed to the flange 3 and a horizontal portion 5 of the pipe 4 is extended transversely with respect to the flange 3 as shown in FIG. 2.
However, for the flange coupling shown in FIG. 2, the radius of a bent portion must be made inevitably large because of the hardness of pipe used normally, so that the horizontal portion 5 of the pipe 4 has a considerably great height h with respect to the flange 3. Therefore, the flange coupling of this type is unsuitable in the case where it is arranged in an extremely limited space near an engine.